The present invention relates to an electronic device, a semiconductor integrated circuit and a data processing system and mainly to a technology effective to be applied to a power supply technology for a battery-driven mobile electronic device.
Standard power supply voltage (such as 3.3 V) has been continuously used for interface between semiconductor chips. On the other hand, pressure resistance of a transistor is decreasing with improvement of micronization. Thus, internal power supply voltage of a large scale integrated circuit (LSI) directs to be lower voltage for every generation. However, the internal power supply voltage is generally different by each chip in such the LSI. Therefore, when the internal power supply is supplied from a power supply on an implemented board, a number of power supplies equal to a given number of chips must be prepared, which increases in cost of a system and size of an implemented area.
As a technology for overcoming those problems, a method is known including the steps of providing a step-down type switching regulator excluding a smoothing circuit including an inductance and a capacitor on a chip, supplying only a standard power supply voltage Vcc for interface on the semiconductor chip and stepping down the voltage on each chip to generate an internal power supply voltage Vddi. The technology is disclosed in Proceedings of Custom Integrated Circuits Conference, May 1997, pp. 587-590 and International Solid-State Circuits Conference, Digest of Technical Papers, Feb. 1999, pp. 156-157.
According to the conventional technology, the internal circuit on the chip is in a stand-by state (for example, a state where a built-in CPU clock is stopped). Thus, when its load current is significantly small, a power conversion efficiency is reduced extremely. As a result, the switching regulator consumes electric power significantly though only a small amount of power needs to be supplied to the internal circuit. This is because AC power consumed by a switching operation for an output MOSFET, which forms an output pulse within the switching regulator is unnegligiblly larger than an output power. Especially in a mobile electronic device, a power loss during such stand-by may reduce a battery lifetime, which is an important performance indicator of the mobile device.
An inventor hereof has realized in Japanese Patent Laid-Open No. 260727/93 and International Patent Publication No. WO 95/09475, through researches of publicly known technologies after the present invention was made, that a power supply had disclosed which combined a switching regulator and a series regulator used them differently through output current in order to reduce power losses. However, the power supply device monitors the output current in order to switch between them, which appears rational. Yet, in an electronic device such as a microcomputer, currents consumed differ largely between the stand-by state where the central processing unit (CPU) and others perform any operations and an operating state where data processing is performed. Especially, a transition time from the stand-by state to the operating state consumes large current rapidly. Therefore, even when the consumed current is monitored for switching the power supply circuit as described above, voltage and/current required for CPU operations cannot be obtained, which may cause an error operation.
The present inventor hereof has focused on that a program-controlled electronic device such as the microcomputer sets an operation mode by itself and considered to attempt higher efficiency in the power supply device by using a control signal generated in the internal portion. Further, for the electronic device, the number of parts tends to be reduced by adopting a circuit element within the semiconductor integrated circuit device. However, The present inventor has notices that it was not always effective to have the circuit element built-in.
It is an object of the present invention to provide an electronic device, a semiconductor integrated circuit and a data processing system, which allow lower power consumption. It is another object of the present invention to provide an electronic device and a data processing circuit, which allows size reduction. Further, it is another object of the present invention to provide an electronic device and a data processing system, which allow size reduction and lower power consumption. These and other objects and novel features of the present invention will be: apparent from description herein and accompanying drawings.
The present invention disclosed herein may be summarized briefly as follows:
For an internal circuit having a first operation mode consuming a first operational current and a second operation mode consuming a second operational current, which is smaller than the first operational current, a first step-down type regulator for stepping down a predefined output power supply voltage from an input power supply voltage and having a current supply ability corresponding to the first operational current of the internal circuit and a second step-down type regulator having a current supply ability corresponding to the second operational current are combined in order to, under the control of a power supply control unit, operate the first step-down type regulator in response to a first control signal instructing the first operation mode in the internal circuit and to operate the second step-down type regulator in response to a second control signal instructing the second operation mode. In this case, the internal circuit and power supply control unit are provided in one semiconductor integrated circuit device so that reduced power consumption and power supply switching in accordance with the operation mode can be achieved.
In an electronic device including a switching regulator for stepping down a predefined output power supply voltage from an input power supply voltage and a semiconductor integrated circuit device including an internal circuit operated by feeding from the switching regulator, the switching regulator may include a driver control circuit formed in the semiconductor integrated circuit device, an output circuit provided in the outside of the semiconductor integrated circuit device for generating an output pulse signal through a drive signal generated by the driver control circuit and an inductance and a capacitor for smoothing the output pulse signal. Thus, a number of pins of the semiconductor integrated circuit device can be decreased regardless of a maximum power supply current, which allows reduction of size and cost in addition to an increase in universality of the regulator circuit.